Vasodepressor activity of renal medulla of spontaneously hypertensive rats.

A parallel study of plasma renin activity, renin content in the kidneys and renal prostaglandin - like activity (PGE2, A2 and F2alpha) in 10 spontaneously hypertensive (SHR) rats (Pkamoto-Aoki), and 10 control normotensive Wistar rats was carried out in order to investigate the role of humoral factors in the pathogenesis of spontaneous hypertension in rats. Peripheral plasma renin activity was assayed by the method of Serebrovskaya, while renal renin activity was estimated by the author's own modification of the method of Serebrovskaya. Prostaglandin-like activity of the renal prostaglandins was assayed by the method of Lee et al. The final evaluation of the PGE2 and PGF2alpha activity was made by biological assay on isolated rat stomach and chicken rectum strips, while PGA2 - like activity was assayed by its vasodepressor effect on the arterial blood pressure of anaesthetized, vagotomized and atropinized rats. It was established that peripheral plasma renin activity was normal, while renin activity in the kidneys of SHR with a long (11 months) duration of hypertension was decreased. Renal prostaglandin activity of SHR did not significantly differ from the controls. It is pointed out that lack of changes in the pressor and depressor renal systems indicates that renal humoral factors are not of prime importance in the patho-genesis of the chronic stage of spontaneous hypertension in rats.